<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html lang = "en">

<head>

<link rel="shortcut icon" href="http://algs4.cs.princeton.edu/favicon.ico">
<link rel="stylesheet"    href="http://algs4.cs.princeton.edu/java.css" type="text/css">

<title>DirectedCycleX.java</title>

<meta HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
<meta NAME="AUTHOR" CONTENT="Robert Sedgewick and Kevin Wayne">
<meta NAME="DESCRIPTION" CONTENT="DirectedCycleX code in Java">
<meta NAME="TITLE" CONTENT="DirectedCycleX code in Java">
<meta NAME="KEYWORDS" CONTENT="DirectedCycleX,java,programming,computer science,algorithm,data structure,program,code">
<meta NAME="ROBOTS" CONTENT="INDEX,FOLLOW">

</head>


<body>
<center><h1>DirectedCycleX.java</h1></center><p><br>

Below is the syntax highlighted version of <a href = "DirectedCycleX.java">DirectedCycleX.java</a>.
<p><br>

<!-- Generator: GNU source-highlight 3.1.6
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span class="comment">/******************************************************************************</span>
<span class="comment"> *  Compilation:  javac DirectedCycleX.java</span>
<span class="comment"> *  Execution:    java DirectedCycleX V E F</span>
<span class="comment"> *  Dependencies: Queue.java Digraph.java Stack.java</span>
<span class="comment"> *</span>
<span class="comment"> *  Find a directed cycle in a digraph, using a nonrecursive, queue-based</span>
<span class="comment"> *  algorithm. Runs in O(E + V) time.</span>
<span class="comment"> *</span>
<span class="comment"> ******************************************************************************/</span>

<span class="preproc">package</span><span class="normal"> edu</span><span class="symbol">.</span><span class="normal">princeton</span><span class="symbol">.</span><span class="normal">cs</span><span class="symbol">.</span><span class="normal">algs4</span><span class="symbol">;</span>

<span class="comment">/**</span>
<span class="comment"> *  The </span><span class="keyword">&lt;tt&gt;</span><span class="comment">DirectedCycleX</span><span class="keyword">&lt;/tt&gt;</span><span class="comment"> class represents a data type for </span>
<span class="comment"> *  determining whether a digraph has a directed cycle.</span>
<span class="comment"> *  The </span><span class="keyword">&lt;em&gt;</span><span class="comment">hasCycle</span><span class="keyword">&lt;/em&gt;</span><span class="comment"> operation determines whether the digraph has</span>
<span class="comment"> *  a directed cycle and, and of so, the </span><span class="keyword">&lt;em&gt;</span><span class="comment">cycle</span><span class="keyword">&lt;/em&gt;</span><span class="comment"> operation</span>
<span class="comment"> *  returns one.</span>
<span class="comment"> *  </span><span class="keyword">&lt;p&gt;</span>
<span class="comment"> *  This implementation uses a nonrecursive, queue-based algorithm.</span>
<span class="comment"> *  The constructor takes time proportional to </span><span class="keyword">&lt;em&gt;</span><span class="comment">V</span><span class="keyword">&lt;/em&gt;</span><span class="comment"> + </span><span class="keyword">&lt;em&gt;</span><span class="comment">E</span><span class="keyword">&lt;/em&gt;</span>
<span class="comment"> *  (in the worst case),</span>
<span class="comment"> *  where </span><span class="keyword">&lt;em&gt;</span><span class="comment">V</span><span class="keyword">&lt;/em&gt;</span><span class="comment"> is the number of vertices and </span><span class="keyword">&lt;em&gt;</span><span class="comment">E</span><span class="keyword">&lt;/em&gt;</span><span class="comment"> is the number of edges.</span>
<span class="comment"> *  Afterwards, the </span><span class="keyword">&lt;em&gt;</span><span class="comment">hasCycle</span><span class="keyword">&lt;/em&gt;</span><span class="comment"> operation takes constant time;</span>
<span class="comment"> *  the </span><span class="keyword">&lt;em&gt;</span><span class="comment">cycle</span><span class="keyword">&lt;/em&gt;</span><span class="comment"> operation takes time proportional</span>
<span class="comment"> *  to the length of the cycle.</span>
<span class="comment"> *  </span><span class="keyword">&lt;p&gt;</span>
<span class="comment"> *  See {</span><span class="type">@link</span><span class="comment"> DirectedCycle} for a recursive version that uses depth-first search.</span>
<span class="comment"> *  See {</span><span class="type">@link</span><span class="comment"> Topological} or {</span><span class="type">@link</span><span class="comment"> TopologicalX} to compute a topological order</span>
<span class="comment"> *  when the digraph is acyclic.</span>
<span class="comment"> *  </span><span class="keyword">&lt;p&gt;</span>
<span class="comment"> *  For additional documentation,</span>
<span class="comment"> *  see </span><span class="keyword">&lt;a</span><span class="normal"> </span><span class="type">href</span><span class="symbol">=</span><span class="string">"http://algs4.cs.princeton.edu/42digraph"</span><span class="keyword">&gt;</span><span class="comment">Section 4.2</span><span class="keyword">&lt;/a&gt;</span><span class="comment"> of</span>
<span class="comment"> *  </span><span class="keyword">&lt;i&gt;</span><span class="comment">Algorithms, 4th Edition</span><span class="keyword">&lt;/i&gt;</span><span class="comment"> by Robert Sedgewick and Kevin Wayne.</span>
<span class="comment"> *</span>
<span class="comment"> *  </span><span class="type">@author</span><span class="comment"> Robert Sedgewick</span>
<span class="comment"> *  </span><span class="type">@author</span><span class="comment"> Kevin Wayne</span>
<span class="comment"> */</span>

<span class="keyword">public</span><span class="normal"> </span><span class="keyword">class</span><span class="normal"> </span><span class="classname">DirectedCycleX</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal">    </span><span class="keyword">private</span><span class="normal"> </span><span class="usertype">Stack&lt;Integer&gt;</span><span class="normal"> cycle</span><span class="symbol">;</span><span class="normal">     </span><span class="comment">// the directed cycle; null if digraph is acyclic</span>

<span class="normal">    </span><span class="keyword">public</span><span class="normal"> </span><span class="function">DirectedCycleX</span><span class="symbol">(</span><span class="usertype">Digraph</span><span class="normal"> G</span><span class="symbol">)</span><span class="normal"> </span><span class="cbracket">{</span>

<span class="normal">        </span><span class="comment">// indegrees of remaining vertices</span>
<span class="normal">        </span><span class="type">int</span><span class="symbol">[]</span><span class="normal"> indegree </span><span class="symbol">=</span><span class="normal"> </span><span class="keyword">new</span><span class="normal"> </span><span class="type">int</span><span class="symbol">[</span><span class="normal">G</span><span class="symbol">.</span><span class="function">V</span><span class="symbol">()];</span>
<span class="normal">        </span><span class="keyword">for</span><span class="normal"> </span><span class="symbol">(</span><span class="type">int</span><span class="normal"> v </span><span class="symbol">=</span><span class="normal"> </span><span class="number">0</span><span class="symbol">;</span><span class="normal"> v </span><span class="symbol">&lt;</span><span class="normal"> G</span><span class="symbol">.</span><span class="function">V</span><span class="symbol">();</span><span class="normal"> v</span><span class="symbol">++)</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal">            indegree</span><span class="symbol">[</span><span class="normal">v</span><span class="symbol">]</span><span class="normal"> </span><span class="symbol">=</span><span class="normal"> G</span><span class="symbol">.</span><span class="function">indegree</span><span class="symbol">(</span><span class="normal">v</span><span class="symbol">);</span>
<span class="normal">        </span><span class="cbracket">}</span>

<span class="normal">        </span><span class="comment">// initialize queue to contain all vertices with indegree = 0</span>
<span class="normal">        </span><span class="usertype">Queue&lt;Integer&gt;</span><span class="normal"> queue </span><span class="symbol">=</span><span class="normal"> </span><span class="keyword">new</span><span class="normal"> Queue</span><span class="symbol">&lt;</span><span class="normal">Integer</span><span class="symbol">&gt;();</span>
<span class="normal">        </span><span class="keyword">for</span><span class="normal"> </span><span class="symbol">(</span><span class="type">int</span><span class="normal"> v </span><span class="symbol">=</span><span class="normal"> </span><span class="number">0</span><span class="symbol">;</span><span class="normal"> v </span><span class="symbol">&lt;</span><span class="normal"> G</span><span class="symbol">.</span><span class="function">V</span><span class="symbol">();</span><span class="normal"> v</span><span class="symbol">++)</span>
<span class="normal">            </span><span class="keyword">if</span><span class="normal"> </span><span class="symbol">(</span><span class="normal">indegree</span><span class="symbol">[</span><span class="normal">v</span><span class="symbol">]</span><span class="normal"> </span><span class="symbol">==</span><span class="normal"> </span><span class="number">0</span><span class="symbol">)</span><span class="normal"> queue</span><span class="symbol">.</span><span class="function">enqueue</span><span class="symbol">(</span><span class="normal">v</span><span class="symbol">);</span>

<span class="normal">        </span><span class="keyword">for</span><span class="normal"> </span><span class="symbol">(</span><span class="type">int</span><span class="normal"> j </span><span class="symbol">=</span><span class="normal"> </span><span class="number">0</span><span class="symbol">;</span><span class="normal"> </span><span class="symbol">!</span><span class="normal">queue</span><span class="symbol">.</span><span class="function">isEmpty</span><span class="symbol">();</span><span class="normal"> j</span><span class="symbol">++)</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal">            </span><span class="type">int</span><span class="normal"> v </span><span class="symbol">=</span><span class="normal"> queue</span><span class="symbol">.</span><span class="function">dequeue</span><span class="symbol">();</span>
<span class="normal">            </span><span class="keyword">for</span><span class="normal"> </span><span class="symbol">(</span><span class="type">int</span><span class="normal"> w </span><span class="symbol">:</span><span class="normal"> G</span><span class="symbol">.</span><span class="function">adj</span><span class="symbol">(</span><span class="normal">v</span><span class="symbol">))</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal">                indegree</span><span class="symbol">[</span><span class="normal">w</span><span class="symbol">]--;</span>
<span class="normal">                </span><span class="keyword">if</span><span class="normal"> </span><span class="symbol">(</span><span class="normal">indegree</span><span class="symbol">[</span><span class="normal">w</span><span class="symbol">]</span><span class="normal"> </span><span class="symbol">==</span><span class="normal"> </span><span class="number">0</span><span class="symbol">)</span><span class="normal"> queue</span><span class="symbol">.</span><span class="function">enqueue</span><span class="symbol">(</span><span class="normal">w</span><span class="symbol">);</span>
<span class="normal">            </span><span class="cbracket">}</span>
<span class="normal">        </span><span class="cbracket">}</span>

<span class="normal">        </span><span class="comment">// there is a directed cycle in subgraph of vertices with indegree &gt;= 1.</span>
<span class="normal">        </span><span class="type">int</span><span class="symbol">[]</span><span class="normal"> edgeTo </span><span class="symbol">=</span><span class="normal"> </span><span class="keyword">new</span><span class="normal"> </span><span class="type">int</span><span class="symbol">[</span><span class="normal">G</span><span class="symbol">.</span><span class="function">V</span><span class="symbol">()];</span>
<span class="normal">        </span><span class="type">int</span><span class="normal"> root </span><span class="symbol">=</span><span class="normal"> </span><span class="symbol">-</span><span class="number">1</span><span class="symbol">;</span><span class="normal">  </span><span class="comment">// any vertex with indegree &gt;= -1</span>
<span class="normal">        </span><span class="keyword">for</span><span class="normal"> </span><span class="symbol">(</span><span class="type">int</span><span class="normal"> v </span><span class="symbol">=</span><span class="normal"> </span><span class="number">0</span><span class="symbol">;</span><span class="normal"> v </span><span class="symbol">&lt;</span><span class="normal"> G</span><span class="symbol">.</span><span class="function">V</span><span class="symbol">();</span><span class="normal"> v</span><span class="symbol">++)</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal">            </span><span class="keyword">if</span><span class="normal"> </span><span class="symbol">(</span><span class="normal">indegree</span><span class="symbol">[</span><span class="normal">v</span><span class="symbol">]</span><span class="normal"> </span><span class="symbol">==</span><span class="normal"> </span><span class="number">0</span><span class="symbol">)</span><span class="normal"> </span><span class="keyword">continue</span><span class="symbol">;</span>
<span class="normal">            </span><span class="keyword">else</span><span class="normal"> root </span><span class="symbol">=</span><span class="normal"> v</span><span class="symbol">;</span>
<span class="normal">            </span><span class="keyword">for</span><span class="normal"> </span><span class="symbol">(</span><span class="type">int</span><span class="normal"> w </span><span class="symbol">:</span><span class="normal"> G</span><span class="symbol">.</span><span class="function">adj</span><span class="symbol">(</span><span class="normal">v</span><span class="symbol">))</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal">                </span><span class="keyword">if</span><span class="normal"> </span><span class="symbol">(</span><span class="normal">indegree</span><span class="symbol">[</span><span class="normal">w</span><span class="symbol">]</span><span class="normal"> </span><span class="symbol">&gt;</span><span class="normal"> </span><span class="number">0</span><span class="symbol">)</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal">                    edgeTo</span><span class="symbol">[</span><span class="normal">w</span><span class="symbol">]</span><span class="normal"> </span><span class="symbol">=</span><span class="normal"> v</span><span class="symbol">;</span>
<span class="normal">                </span><span class="cbracket">}</span>
<span class="normal">            </span><span class="cbracket">}</span>
<span class="normal">        </span><span class="cbracket">}</span>

<span class="normal">        </span><span class="keyword">if</span><span class="normal"> </span><span class="symbol">(</span><span class="normal">root </span><span class="symbol">!=</span><span class="normal"> </span><span class="symbol">-</span><span class="number">1</span><span class="symbol">)</span><span class="normal"> </span><span class="cbracket">{</span>

<span class="normal">            </span><span class="comment">// find any vertex on cycle</span>
<span class="normal">            </span><span class="type">boolean</span><span class="symbol">[]</span><span class="normal"> visited </span><span class="symbol">=</span><span class="normal"> </span><span class="keyword">new</span><span class="normal"> </span><span class="type">boolean</span><span class="symbol">[</span><span class="normal">G</span><span class="symbol">.</span><span class="function">V</span><span class="symbol">()];</span>
<span class="normal">            </span><span class="keyword">while</span><span class="normal"> </span><span class="symbol">(!</span><span class="normal">visited</span><span class="symbol">[</span><span class="normal">root</span><span class="symbol">])</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal">                visited</span><span class="symbol">[</span><span class="normal">root</span><span class="symbol">]</span><span class="normal"> </span><span class="symbol">=</span><span class="normal"> </span><span class="keyword">true</span><span class="symbol">;</span>
<span class="normal">                root </span><span class="symbol">=</span><span class="normal"> edgeTo</span><span class="symbol">[</span><span class="normal">root</span><span class="symbol">];</span>
<span class="normal">            </span><span class="cbracket">}</span>

<span class="normal">            </span><span class="comment">// extract cycle</span>
<span class="normal">            cycle </span><span class="symbol">=</span><span class="normal"> </span><span class="keyword">new</span><span class="normal"> Stack</span><span class="symbol">&lt;</span><span class="normal">Integer</span><span class="symbol">&gt;();</span>
<span class="normal">            </span><span class="type">int</span><span class="normal"> v </span><span class="symbol">=</span><span class="normal"> root</span><span class="symbol">;</span>
<span class="normal">            </span><span class="keyword">do</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal">                cycle</span><span class="symbol">.</span><span class="function">push</span><span class="symbol">(</span><span class="normal">v</span><span class="symbol">);</span>
<span class="normal">                v </span><span class="symbol">=</span><span class="normal"> edgeTo</span><span class="symbol">[</span><span class="normal">v</span><span class="symbol">];</span>
<span class="normal">            </span><span class="cbracket">}</span><span class="normal"> </span><span class="keyword">while</span><span class="normal"> </span><span class="symbol">(</span><span class="normal">v </span><span class="symbol">!=</span><span class="normal"> root</span><span class="symbol">);</span>
<span class="normal">            cycle</span><span class="symbol">.</span><span class="function">push</span><span class="symbol">(</span><span class="normal">root</span><span class="symbol">);</span>
<span class="normal">        </span><span class="cbracket">}</span>

<span class="normal">        </span><span class="keyword">assert</span><span class="normal"> </span><span class="function">check</span><span class="symbol">();</span>
<span class="normal">    </span><span class="cbracket">}</span>

<span class="normal">    </span><span class="comment">/**</span>
<span class="comment">     * Returns a directed cycle if the digraph has a directed cycle, and </span><span class="keyword">&lt;tt&gt;</span><span class="comment">null</span><span class="keyword">&lt;/tt&gt;</span><span class="comment"> otherwise.</span>
<span class="comment">     * </span><span class="type">@return</span><span class="comment"> a directed cycle (as an iterable) if the digraph has a directed cycle,</span>
<span class="comment">     *    and </span><span class="keyword">&lt;tt&gt;</span><span class="comment">null</span><span class="keyword">&lt;/tt&gt;</span><span class="comment"> otherwise</span>
<span class="comment">     */</span>
<span class="normal">    </span><span class="keyword">public</span><span class="normal"> </span><span class="usertype">Iterable&lt;Integer&gt;</span><span class="normal"> </span><span class="function">cycle</span><span class="symbol">()</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal">        </span><span class="keyword">return</span><span class="normal"> cycle</span><span class="symbol">;</span>
<span class="normal">    </span><span class="cbracket">}</span>

<span class="normal">    </span><span class="comment">/**</span>
<span class="comment">     * Does the digraph have a directed cycle?</span>
<span class="comment">     * </span><span class="type">@return</span><span class="comment"> </span><span class="keyword">&lt;tt&gt;</span><span class="comment">true</span><span class="keyword">&lt;/tt&gt;</span><span class="comment"> if the digraph has a directed cycle, </span><span class="keyword">&lt;tt&gt;</span><span class="comment">false</span><span class="keyword">&lt;/tt&gt;</span><span class="comment"> otherwise</span>
<span class="comment">     */</span>
<span class="normal">    </span><span class="keyword">public</span><span class="normal"> </span><span class="type">boolean</span><span class="normal"> </span><span class="function">hasCycle</span><span class="symbol">()</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal">        </span><span class="keyword">return</span><span class="normal"> cycle </span><span class="symbol">!=</span><span class="normal"> </span><span class="keyword">null</span><span class="symbol">;</span>
<span class="normal">    </span><span class="cbracket">}</span>

<span class="normal">    </span><span class="comment">// certify that digraph has a directed cycle if it reports one</span>
<span class="normal">    </span><span class="keyword">private</span><span class="normal"> </span><span class="type">boolean</span><span class="normal"> </span><span class="function">check</span><span class="symbol">()</span><span class="normal"> </span><span class="cbracket">{</span>

<span class="normal">        </span><span class="keyword">if</span><span class="normal"> </span><span class="symbol">(</span><span class="function">hasCycle</span><span class="symbol">())</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal">            </span><span class="comment">// verify cycle</span>
<span class="normal">            </span><span class="type">int</span><span class="normal"> first </span><span class="symbol">=</span><span class="normal"> </span><span class="symbol">-</span><span class="number">1</span><span class="symbol">,</span><span class="normal"> last </span><span class="symbol">=</span><span class="normal"> </span><span class="symbol">-</span><span class="number">1</span><span class="symbol">;</span>
<span class="normal">            </span><span class="keyword">for</span><span class="normal"> </span><span class="symbol">(</span><span class="type">int</span><span class="normal"> v </span><span class="symbol">:</span><span class="normal"> </span><span class="function">cycle</span><span class="symbol">())</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal">                </span><span class="keyword">if</span><span class="normal"> </span><span class="symbol">(</span><span class="normal">first </span><span class="symbol">==</span><span class="normal"> </span><span class="symbol">-</span><span class="number">1</span><span class="symbol">)</span><span class="normal"> first </span><span class="symbol">=</span><span class="normal"> v</span><span class="symbol">;</span>
<span class="normal">                last </span><span class="symbol">=</span><span class="normal"> v</span><span class="symbol">;</span>
<span class="normal">            </span><span class="cbracket">}</span>
<span class="normal">            </span><span class="keyword">if</span><span class="normal"> </span><span class="symbol">(</span><span class="normal">first </span><span class="symbol">!=</span><span class="normal"> last</span><span class="symbol">)</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal">                System</span><span class="symbol">.</span><span class="normal">err</span><span class="symbol">.</span><span class="function">printf</span><span class="symbol">(</span><span class="string">"cycle begins with %d and ends with %d</span><span class="specialchar">\n</span><span class="string">"</span><span class="symbol">,</span><span class="normal"> first</span><span class="symbol">,</span><span class="normal"> last</span><span class="symbol">);</span>
<span class="normal">                </span><span class="keyword">return</span><span class="normal"> </span><span class="keyword">false</span><span class="symbol">;</span>
<span class="normal">            </span><span class="cbracket">}</span>
<span class="normal">        </span><span class="cbracket">}</span>


<span class="normal">        </span><span class="keyword">return</span><span class="normal"> </span><span class="keyword">true</span><span class="symbol">;</span>
<span class="normal">    </span><span class="cbracket">}</span>


<span class="normal">    </span><span class="keyword">public</span><span class="normal"> </span><span class="keyword">static</span><span class="normal"> </span><span class="type">void</span><span class="normal"> </span><span class="function">main</span><span class="symbol">(</span><span class="normal">String</span><span class="symbol">[]</span><span class="normal"> args</span><span class="symbol">)</span><span class="normal"> </span><span class="cbracket">{</span>

<span class="normal">        </span><span class="comment">// create random DAG with V vertices and E edges; then add F random edges</span>
<span class="normal">        </span><span class="type">int</span><span class="normal"> V </span><span class="symbol">=</span><span class="normal"> Integer</span><span class="symbol">.</span><span class="function">parseInt</span><span class="symbol">(</span><span class="normal">args</span><span class="symbol">[</span><span class="number">0</span><span class="symbol">]);</span>
<span class="normal">        </span><span class="type">int</span><span class="normal"> E </span><span class="symbol">=</span><span class="normal"> Integer</span><span class="symbol">.</span><span class="function">parseInt</span><span class="symbol">(</span><span class="normal">args</span><span class="symbol">[</span><span class="number">1</span><span class="symbol">]);</span>
<span class="normal">        </span><span class="type">int</span><span class="normal"> F </span><span class="symbol">=</span><span class="normal"> Integer</span><span class="symbol">.</span><span class="function">parseInt</span><span class="symbol">(</span><span class="normal">args</span><span class="symbol">[</span><span class="number">2</span><span class="symbol">]);</span>
<span class="normal">        </span><span class="usertype">Digraph</span><span class="normal"> G </span><span class="symbol">=</span><span class="normal"> DigraphGenerator</span><span class="symbol">.</span><span class="function">dag</span><span class="symbol">(</span><span class="normal">V</span><span class="symbol">,</span><span class="normal"> E</span><span class="symbol">);</span>

<span class="normal">        </span><span class="comment">// add F extra edges</span>
<span class="normal">        </span><span class="keyword">for</span><span class="normal"> </span><span class="symbol">(</span><span class="type">int</span><span class="normal"> i </span><span class="symbol">=</span><span class="normal"> </span><span class="number">0</span><span class="symbol">;</span><span class="normal"> i </span><span class="symbol">&lt;</span><span class="normal"> F</span><span class="symbol">;</span><span class="normal"> i</span><span class="symbol">++)</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal">            </span><span class="type">int</span><span class="normal"> v </span><span class="symbol">=</span><span class="normal"> StdRandom</span><span class="symbol">.</span><span class="function">uniform</span><span class="symbol">(</span><span class="normal">V</span><span class="symbol">);</span>
<span class="normal">            </span><span class="type">int</span><span class="normal"> w </span><span class="symbol">=</span><span class="normal"> StdRandom</span><span class="symbol">.</span><span class="function">uniform</span><span class="symbol">(</span><span class="normal">V</span><span class="symbol">);</span>
<span class="normal">            G</span><span class="symbol">.</span><span class="function">addEdge</span><span class="symbol">(</span><span class="normal">v</span><span class="symbol">,</span><span class="normal"> w</span><span class="symbol">);</span>
<span class="normal">        </span><span class="cbracket">}</span>

<span class="normal">        StdOut</span><span class="symbol">.</span><span class="function">println</span><span class="symbol">(</span><span class="normal">G</span><span class="symbol">);</span>


<span class="normal">        </span><span class="usertype">DirectedCycleX</span><span class="normal"> finder </span><span class="symbol">=</span><span class="normal"> </span><span class="keyword">new</span><span class="normal"> </span><span class="function">DirectedCycleX</span><span class="symbol">(</span><span class="normal">G</span><span class="symbol">);</span>
<span class="normal">        </span><span class="keyword">if</span><span class="normal"> </span><span class="symbol">(</span><span class="normal">finder</span><span class="symbol">.</span><span class="function">hasCycle</span><span class="symbol">())</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal">            StdOut</span><span class="symbol">.</span><span class="function">print</span><span class="symbol">(</span><span class="string">"Directed cycle: "</span><span class="symbol">);</span>
<span class="normal">            </span><span class="keyword">for</span><span class="normal"> </span><span class="symbol">(</span><span class="type">int</span><span class="normal"> v </span><span class="symbol">:</span><span class="normal"> finder</span><span class="symbol">.</span><span class="function">cycle</span><span class="symbol">())</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal">                StdOut</span><span class="symbol">.</span><span class="function">print</span><span class="symbol">(</span><span class="normal">v </span><span class="symbol">+</span><span class="normal"> </span><span class="string">" "</span><span class="symbol">);</span>
<span class="normal">            </span><span class="cbracket">}</span>
<span class="normal">            StdOut</span><span class="symbol">.</span><span class="function">println</span><span class="symbol">();</span>
<span class="normal">        </span><span class="cbracket">}</span>

<span class="normal">        </span><span class="keyword">else</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal">            StdOut</span><span class="symbol">.</span><span class="function">println</span><span class="symbol">(</span><span class="string">"No directed cycle"</span><span class="symbol">);</span>
<span class="normal">        </span><span class="cbracket">}</span>
<span class="normal">        StdOut</span><span class="symbol">.</span><span class="function">println</span><span class="symbol">();</span>
<span class="normal">    </span><span class="cbracket">}</span>

<span class="cbracket">}</span>

<span class="comment">/******************************************************************************</span>
<span class="comment"> *  Copyright 2002-2015, Robert Sedgewick and Kevin Wayne.</span>
<span class="comment"> *</span>
<span class="comment"> *  This file is part of algs4.jar, which accompanies the textbook</span>
<span class="comment"> *</span>
<span class="comment"> *      Algorithms, 4th edition by Robert Sedgewick and Kevin Wayne,</span>
<span class="comment"> *      Addison-Wesley Professional, 2011, ISBN 0-321-57351-X.</span>
<span class="comment"> *      </span><span class="url">http://algs4.cs.princeton.edu</span>
<span class="comment"> *</span>
<span class="comment"> *</span>
<span class="comment"> *  algs4.jar is free software: you can redistribute it and/or modify</span>
<span class="comment"> *  it under the terms of the GNU General Public License as published by</span>
<span class="comment"> *  the Free Software Foundation, either version 3 of the License, or</span>
<span class="comment"> *  (at your option) any later version.</span>
<span class="comment"> *</span>
<span class="comment"> *  algs4.jar is distributed in the hope that it will be useful,</span>
<span class="comment"> *  but WITHOUT ANY WARRANTY; without even the implied warranty of</span>
<span class="comment"> *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the</span>
<span class="comment"> *  GNU General Public License for more details.</span>
<span class="comment"> *</span>
<span class="comment"> *  You should have received a copy of the GNU General Public License</span>
<span class="comment"> *  along with algs4.jar.  If not, see </span><span class="url">http://www.gnu.org/licenses.</span>
<span class="comment"> ******************************************************************************/</span>
</tt></pre>

<script type="text/javascript">
var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www.");
document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E"));
</script>
<script type="text/javascript">
try {
var pageTracker = _gat._getTracker("UA-10811519-2");
pageTracker._trackPageview();
} catch(err) {}</script>

</body>

<p><br><address><small>
Last updated: Mon Mar 21 10:51:08 EDT 2016.
</small></address>

</html>
